Such dispensing assemblies with so-called double, concentric pumps are generally known in the prior art and are used for dispensing many kinds of liquid components from containers. Such liquid components are not particularly limited and vary from aqueous liquid components to paste-like materials.
Examples of components to be dispensed are, for example, adhesives with a hardener, paints with a hardener, cosmetic products with reactive components, detergents with reactive components etc.
The ratio between the quantities of the components to be dispensed can be set as desired by a suitable choice of the dimensions of the parts in question.
The outflow openings for the components in question can be in the form of individual outflow openings, but they can also be in the form of a common outflow opening, with the interposition of a mixing chamber section or otherwise.
All known dispensing assemblies have the major disadvantage that partial vacuum possibly occurring outside the outflow opening causes an inadequate seal to be obtained between the concentric inner and outer piston. This can occur, for example, in an aircraft. In that case, material may be sucked out of the outer piston chamber, through between the pistons, and consequently out of the container for the particular component which may be connected to the outlet of the outer piston chamber, and out of the outflow opening. This is, of course, undesirable. Constituents are in fact often dispensed with such dispensing assemblies in practice, which are sticky after drying or otherwise. When there is accidental outflow of such constituents, the subsequent functioning of the dispensing assembly may be seriously impeded, if not rendered impossible.
The control part used in the case of such dispensing assemblies is generally a push-button on the dispensing assembly, which push-button interacts with both pumps. It is undesirable for said button to be soiled with material for dispensing, since a user operates the dispensing assembly by pressing with a finger on the push-button.
Moreover, the entire assembly is often shut off by a sealing cap or sealing cover, which can also be undesirably soiled by the abovementioned escaping component.